Radio beacon



ay 14, 19426. w. D. MGGUIGAN v 4005i? RADIO BEACON Filed NOV. 15, 1945 WML/,4M 0. MMU/GAN May i4, 1946. wf D. MCGUIGN- RADIO BEACON Filed Nov. 15, 1943 2 Sheets-Sheet 2 IN V EN TOR.

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Sol/RCE Patented May 14, 1946 2,400,127 RADIO BEACON William D. McGuigan, New York, N. Y., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application November 15, 1943, Serial No. 510,265

(Cl. Z50-11) 12 Claims.

This invention relates to radio beacons and more particularly to radio beacons designed principally for use with indicating receivers having automatic volume control.

In radio beacon systems provided with automatic volume control radio receivers, the apparent sharpness of the course may be controlled byproviding a radio beacon wherein the carrier level and the audio frequency level of the signals varies differently in amplitude in different directions about the beacon.

It is an object of my invention to provide a radio beacon which will produce a high degree of sharpness of course indication.

It is a further object of my invention to provide a radio beacon system in which there is apparent a large change in average signal level in the indicator with departure from course.

It is a still further object of my invention to provide a radio beacon system in which the carrier level of the sideband level of the signals is alternately reversed in phase and in which these levels Aare diierent one from another in different; directions.

According to a feature of my invention, I provide an arrangement for producing at carrier frequency a given radiation pattern having a minimum in a predetermined direction. This minimum must be maintained at a level above zero for proper operation of the system. In conjunction with the carrier pattern, I provide a sideband pattern having a maximum aligned substantially with the minimum of the carrier pattern. These two patterns are then alternately reversed in phase to provide a pair of intersecting patterns dening a course line. On a craft using this beacon is provided a receiver having an automatic volume control, the gain of the receiver being varied proportionately with the level of the carrier energy so that the volume of the output signals will be controlled largely by the carrier energy and the directive pattern of the sideband energy. Thus, the sharpness of the course indication may be controlled by controlling the shape and position of the carrier and sideband patterns independently.

Since the course indicating signals need not reach 100% modulation level in any direction around the beacon, voice signals may be applied to modulate the carrier energy, the voice signal modulation being maintained at such a value as to produce not more than 100% modulation in combination with the course signals.

A better understanding of my invention and the objects and features thereof may be had by reference to the accompanying drawings, in which: p

Fig. 1 illustrates in block diagram a simplified radio beacon circuit in accordance with my invention;

Fig. 2 illustrates in block diagram a circuit arrangement of a modied radio beacon in accordance with my invention, together with a receiver to be used therewith;

Fig. 3 illustrates a typical radiation pattern of the carrier and sideband signals from a radio beacon in accordance with my invention;

Fig.4 illustrates the resultant indication produced in the output of a receiver by the signal patterns of Fig. 3; and

Fig.'5 illustrates a further modification of my invention showing its application to a known type of radio beacon.

Turning rst to Fig. 1, I0 represents a radio frequency source supplying the carrier energy. Energy from source l0 is amplified in radio frequency amplifier II and applied therefrom over phase shifter I3 and line I4 and the contacts of switch I2 to the carrier frequency radiating means including antennas I5 and I6. By adjusting the feeding point of the coupling to line I4, a desired phase relation between energy in antennas I5 and I6 may be provided. Thus, for example, a radiation pattern of the type shown at 60, Fig. 3, may be obtained.

At the same time, both radio frequency energy from. source I0 and signal energy from signal source I7 are applied to sideband generator I8. The .signal from source II may be any suitable audio frequency tone, for example, 1020 cycles per second. Sideband generator I3 may be of the normal balanced modulator type so as to produce sidebands of energy and suppress substantially all the carrier therefrom. The sideband energy from generator I8 is similarly fed over switch I 9 and line 20 to the sideband radiatingmeans including antennas 2| and 22. The phasing of the sideband energy fed to antennas 2| vand 22 is adjusted to produce a radiation pattern diifering from the carrier radiation pattern and having a maximum substantially aligned with the minimum of the carrier radiation pattern, as indicated by curve 'I0 of Fig. 3. Likewise, the level of this sideband signal is maintained at a value below the minimum value of the carrier energy. To this end sideband generator I8 may be made adjustable and for the amplication in radio frequency amplifier I0, suitably controlled.

TheV two radiation patterns are simultaneously indicated. Thus, a resultant intersectingbeacon pattern is provided in which the carrier energy and the sideband energy diier relatively to rone another as a plane travels around the beacon. The difference in signal level'and carrier level produces eiectively a difference'in percentage and the maximum of the sideband pattern. Ac-

cordingly, this difference in level will determine the percentage modulation permissible in the voice signals.

In Fig. 2 is also illustrated a receiver suitable 'for use with beacon arrangements-such as shown in Fig. 1 or Fig. 2. This receiver includes a receiving antenna 5D and receiver-detector 5| provided with an automatic volume control lead 52 serving to control the level of energy in the receiver in accordance with the carrier energy level received. Such automatic volume control systems are Well known in the art and need not be shown in detail for the purpose of illustrating this invention. In'the output of the receiver is provided a signal lter 53 and a signal indicator modulation of the receivedsignals.A 'u With anv automatic volume` control on the -receiver -controlling the gain of the amplifier in accordance.A 1

with carrier level, two resultant effective patterns, such as shown at 80 and 8| of Fig. 4 are produced, having intersections with one another at 82 and 83. Y

It is clear that in place of two antennas, such as shown at I5 and I6, some other form of 'directive radiator may be used and likewise a diierent form of radiating means may be `used for the. sideband energy in place of the antennas shown at 2| and 22.

In Fig. 2 is shown a further embodiment of my invention wherein two antennas are used simultaneously to produce both the carrier and the sideband radiation patterns. In this arrangement, radio frequency source 30 is coupled to amplier 3| and over switch 32, line 33 and balancing bridges 34 and 35 to the antennas 36 and 31. The phasing of the energy supplied to antennas 36 and 31 is adjusted to provide the desired radiation pattern. Simultaneously, energy from source 30 is fed over phase shifter '39 to sideband generator 40 together with signal energy from signal source 38. From the output of sideband generator 4|) the sideband energy is applied over switch 4|, line 42 and bridges 34 and 35 to the same antennas 36 and 31. The phase of the sideband energy supplied to antennas 36 and 31 from the sideband generator is adjusted, however, to produce the same or a differently shaped radiation pattern from that produced by the carrie;` energy. Likewise, the amplitude of this sideband energy supplied Ato the. radiators is maintained at a level below that supplied from amplifier 3| and described in connection with Fig. l.

vBalancing networks 43 and 44 are connected to the terminals of bridges 34 and 35, respectively, lto maintain proper balance in the bridges. The carrier and sideband radiation patterns are alternately reversed by keyer 46 and keying relay coil 45 serving to operate switches 32 and 4|.

If desired, voice signals from voice source 41v may be applied to modulate the radio frequency energy in amplifier 3| lso that the carrier energy will also have voice signal modulation. 'I'he degree cf modulation of the carrier by the voice energy is determined by the maximum effective percentage modulation produced by the carrier and sideband patterns, i. e. by the minimum difference in level between the sideband radiation pattern and the carrier radiation pattern. It is clear that, since the directive patterns for the carrier and the sidebands are different, the per-V centage modulation of the beacon signals will vary around the beacon. The highest percentage modulation of the beacon signal and carrier is in line with the minimum of the carrier pattern 54'which'may be simply a pair of head phones. Also, in the output of receiver 5| is provided audio circuit 55 coupled to a voice reproducer 56 for reproducing voice modulation signals.

In addition to the circuit elements and operational .characteristics outlined above, it ris desirable that the phase of the sideband signals, measured with respect to the suppressed carrier with which they were generated,and the carrier frequency energy be substantially cophasal or in phase opposition. If the sideband energy is substantially in phase with respect to the carrier frequency energy in the receiver, harmonic distortion will take place and itwlll be diflicult to filter out the beacon indicating signals. To this end, phase shifter I3 of Fig. l and phase shifter 39 of Fig. 2 are provided. These .phase yShifters are adjusted so that the effective carrier energy at the antennas is substantially in phase with the sideband energy supplied to the'antennas. l

The radiation patterns shown in Figsg and 4 are calculated for a pair of antennas similar to that shown in Fig. 2. In this particular e'xample, antennas 136 and 31 are spaced apart by distance equal to 45 electrical degrees andthe carrier energy is fed to these antennas in 90 phase relationship one to the other. With this energization patterns such as shown at 60, lily are produced having intersections at points 62 and 53. The energy supplied from the sideband generator to the two antennas 3|; and 31 are phased apart withrespect to one another producing the modiiied iigure 8 pattern defined by curves 10 and 1|, having intersections at B2, 83. With this arrangement it is found that phase shifter 39 should be adjusted to provide a phase shift of substantially 45"v inthe carrier energy, as supplied to the radio frequencyy amplifier and the sideband generator in order to provide the proper phase relationship o'fthe carrier and sideband energy. It should be clear, however, that this phase shift may bev obtained equally well by placing the phase shifter in the output ofV the radio frequency amplifier, if clesired, as shown in Fig. l or by placing the phase shifter in the output line from sideband generator40. v -A' With the carrier and sideband patterns of Fig. 3 Vthe eiective receiver indication patterns will be as shown in Fig. 4 at 80, 8| having intersections at points 82 and 183. AThus, ,with` the arrangement outlined above, 'a course sharpnessr of substantially Vone decibel per degree -departure from course may' be obtained with ia simple two-antenna array. It is clear that the directive pattern from either of the arrays rmay be modied over'a wide range Withoutdeparting from the Ascope of my invention. It is `essential, however, that the carrier frequency pattern antennas for the carrier frequency must be'V spaced apart a distance less than`180 electricall degrees. Also, the phase of the energy supplied to these units must be such that there will be no zero nulls in the directive radiation pattern. It is also clear that precautions must be taken to prevent multiple course production due to lobes of the sideband radiation pattern co-acting with the carrier radiation pattern.

In Fig. is disclosed the application of my invention to a previously proposed type of radio beacon system. The radiating portion of the system comprises a central antenna 90 flanked on opposite sides with antenna units 9| and 92 coupled together in phase opposition and coupled to an unsymmetrically spaced antenna arrangement including antennas 93 and 94. Energy is fed to the antenna 90 and to the other antenna units 9| to 94 from opposite diagonal points on a bridge network 95. To the other bridge terminals are connected radio frequency amplifier 9S and sideband generator 91, both supplied from a common radio frequency source 98. The energy from sideband generator 91 is reduced to a sufliciently low level with respect to the carrier energy from amplier 96 so that the sideband radiation pattern from the antenna system will at no place provide more than 100% modulation. Because of the transposition in one arm of the bridge 95, the sideband and carrier patterns produced in the antenna array will be of opposite spaced distribution. Viewed in one light, this radio beacon may be considered as a special form of the beacon arrangement shown in Fig. 2 but with a more complex antenna array. In order to reverse the patterns to provide the desired beacon arrangement, the keyer 99 is provided.

It is clear that in accordance with my invention I have provided a simplified radio beacon which will produce a desired sharpness on course with a simple radiating system.

While I have described my invention in conjunction with specic forms of the apparatus, it is to be understood that this is given only by way of example and that my invention contemplates many modications within the scope thereof as set forth in the objects of my invention and the appended claims.

What is claimed is:

l. A radio beacon comprising means for producing at carrier frequency a radiation pattern having a minimum radiation in a given direction, means for producing a signal sideband radiation pattern having a maximum radiation in said given direction, said sideband maximum being lower in amplitude than said carrier minimum, and means for alternately and simultaneously shifting similarly in phase said sideband and said radiation patterns,

2. A radio beacon according to claim 1, further comprising means for adjusting the relative phase of said carrier frequency energy and said sideband energy.

3. A radio beacon comprising two antenna means, means for energizing said two antenna means with carrier frequency energy, means for phasing the carrier frequency supplied to said two antenna means to produce a radiation pattern having a minimum in a predetermined direction, means for simultaneously energizing said two antenna means with sideband energy, means for phasing the sideband energy supplied to said two antenna means to produce a sideband radiation pattern having a maximum in said predetermined direction, means for adjusting the relative amplitudes of-'said carrier and sidebandv energy to maintain said sideband energy maximum at a lower value than said carrier minimum, and means for simultaneously reversing the phase of said carrier and sideband energy'supplied to said alternate means.

4. A radio beacon according to claim 3, further comprising means for adjusting the relative phase between said'c'arrierfrequency energy and said sideband energy.-

5. A radio beacon according to claim 3, further comprising a voice frequency source, and means for modulating said carrier frequency energy with energy from said voice source.

6. A radio beacon guiding system having a receiver provided with automatic volume control variable proportionally With the level of carrier of the received signals, and a course indicator for receiving and comparing the course signals, in combination with a radio beacon, comprising two antenna means, means for energizing said two antenna means with carrier frequency energy, means for phasing the carrier frequency supplied to said two antenna means to produce a radiation pattern having a minimum in a predetermined direction, means for simultaneously energizing said two antenna means with sideband energy, means for phasing the sideband energy supplied to said two antenna means to produce a sideband radiation pattern having a maximum in said predetermined direction, means for adjusting the relative amplitudes of said carrier and sideband energy to maintain said sideband energy maximum at a lower value than said carrier minimum, and means for simultaneously reversing the phase of said carrier and sideband energy supplied to said alternate means, whereby the course indications are relatively sharp.

7. A radio beacon guiding system having a receiver provided with automatic volume control variable proportionally with the level of carrier of the received signals, and a course indicator for receiving and comparing the course signals, in combination with a radio beacon, comprising means for producing a radiation pattern at carrier` frequency having a minimum radiation in a given direction, means for producing a signal sideband radiation pattern having a maximum radiation in said given direction, said sideband maximum being lower in amplitude than said carrier minimum, and means for alternately and simultaneously reversing said sideband and said radiation patterns, whereby the course indications are relatively sharp.

8. A radio beacon system according to claim 7, further comprising phase control means in said beacon for controlling the relative phase displacement of said carrier frequency energy and said sideband energy.

9. A radio beacon system according to claim 7, further comprising voice signal output means and means for segregating said course signals and said voice signals in said receiver, and a voice frequency source, and means for modulating said carrier frequency with said voice signals at said beacon.

10. A method of providing a beacon for course indication, comprising producing a radiation patternat carrier frequency having a minimum radiation in a given direction, producing a signal sideband radiation pattern having a maximum radiation in said given direction, said side- 11. A method according to claim 10, furthery comprising adjusting the relativel phase of said sideband and said carrier frequency energies to provide substantially cophasal relationship in said radiation pattern.

12. A method of providing a radio beacon by radiation from two antenna means spaced apart less than 180 electrical degrees, comprising energizing said antenna means with carrier energy, phasing the carrier energy supplied to said antenna means to provide a radiation pattern having` av minimum greaterrthan zero in a predetermine'dr'direction, simultaneously energizing said twoantenna lmeans with sideband energy, vphasingsaid sideband energy supplied to said two antenna means to provide a radiation pattern having a maximum aligned with said minimum, controlling the relative amplitudes of said carrier and sideband energy so that said maximum is less thanv said minimum, andalternately simultanefously reversing the phase of the energies applied to said two antenna means.

WILLIAM D. McGnLJIGnm.l 

